The effects of chronic progressive neurologic disorders in adults and children were evaluated by a broad range of neuropsychologic tests evaluating brain-behavior relations. A neuropsychologic profile was plotted for patients with Alzheimer's (AD). Huntington's (HD), or Parkinson's (PD) diseases. The evaluations extended into memory, learning and perception, applying standard and experimental tasks to identify functional changes accompanying the aging processes. The results implicated dopamine deficiencies and frontal pathophysiology in PD, most notably, losses in executive capabilities and visuospatial and generic memory functions. With HD patients, perceptuomotor capacity and the ability to manipulate spatial information were affected whereas spatial discrimination was relatively intact. With a dichotic task, AD patients did poorer and were unable to selectively attend to serial information. The behavioral data extend neuropathologic impressions of degeneration of the frontal striatal system in HD and temporoparietal, cortical involvement in AD.